Radar Grid Types
There are four available grid types for radars (since 0.17.4), which are as follows:

Square (Optimal)

Square (Intersecting)

Square (Double intersecting)

Quasihexagonal (Scanning Radar)
Dedicated for radars in mod “Scanning Radar”, which have circular coverage. See below.
Support for mod "Scanning Radar"
In mod Scanning Radar, those radars perform polar sweep, giving circular coverage area. A square grid for vanilla radars is no longer good for full coverage of the map.
Mathematically, a regular hexagonal grid would be used for tiling. Yet, a bit of asymmetry in scanning radar locations would actaully be better, due to the chunk calculations in the game. This mod perform a careful calculation (which is much more complicated than square grid) to give the optimal quasiregular hexagonal grid, in the sense that it gives least overlapping while not leaving any holes in the coverage.
To activate the quasihexagonal grid calculation, under "Options" → "Mod settings" → "Per Player", select "Quasihexagonal (Scanning Radar)" within "Radar grid type". Input the number of chunks (equals to value of signal R divided by 32) to the field of "Radar reveal radius". After that, first calibrate like the other radar grids.
The following screenshot demonstrates placement by aligning to such grid. It is using radius of 10 chunks (signal R = 10×32 = 320). It also has near radius of 6 chunks (signal N = 6×32 = 192), to highlight radar locations better.